Automatic Node Distribution and Alignment
Default transforms:
You can rotate and scale multiple nodes as you can objects with Manipulate origins enabled:

You can use the usual tricks, e.g. press S X (or Y) 0 to align nodes along a particular axis. Note that the &quot;origins&quot; of all nodes are at the top left.
Node wrangler
This addon comes bundled with blender by default, but you'll have to enable it. It comes packed with all kinds of workflow accelerating functions and shortcuts; press ⎈ CtrlSpace in the node editor to get a menu of all of them.
One such function (⇧ Shift=) aligns the selected nodes:

NodeArrange
An experimental script recently featured which completely rearranges an entire node tree: